Previously, there is a case where a refrigeration cycle for an in-vehicle air conditioning apparatus includes: primary and secondary evaporators, which cool inside air of a cabin of the vehicle; and first and second blowers, which generate a flow of the inside air of the cabin that passes through the primary and secondary evaporators. The patent literature 1 discloses a technique, in which the primary and secondary evaporators are connected in parallel between a refrigerant inlet of a compressor and a refrigerant outlet of a condenser in the above-described type of refrigeration cycle.
According to this technique, first and second electromagnetic valves are provided to close refrigerant inlets of the primary and secondary evaporators. Therefore, a flow of lubricant oil to one of the primary and secondary evaporators can be limited by closing the refrigerant inlet of the one of the primary and secondary evaporators through the corresponding one of the first and second electromagnetic valves. Therefore, at the time of stopping one of the first and second blowers, which corresponds to the one of the primary and secondary evaporators, accumulation of the lubricant oil at the one of the primary and secondary evaporators can be limited by closing the corresponding one of the first and second electromagnetic valves.
In contrast, the patent literature 2 discloses another technique of performing an oil return control operation where the lubricant oil, which is accumulated in the one (hereinafter referred to as a stopped evaporator) of the primary and secondary evaporators, which corresponds to the stopped one of the first and second blowers, to the compressor.
According to this technique, first and second expansion valves are respectively provided to the refrigerant inlets of the primary and secondary evaporators. The oil return control operation repeats turning on and turning off of the compressor several times within a short period of time. The oil return control operation uses the phenomenon of that the expansion valve of the stopped evaporator among the first and second expansion valves is temporarily opened in response to the turning on and turning off of the compressor. When the expansion valve is opened, a flow of the refrigerant from the refrigerant outlet of the compressor to the stopped evaporator through the expansion valve is generated. In this way, the lubricant oil, which is accumulated in the stopped evaporator, can be returned to the inlet of the compressor.